The present invention relates to semiconductor devices, and, more particularly, to a semiconductor device for electro-optic applications and a corresponding semiconductor laser device. The semiconductor device includes a rare-earth ions doped P/N junction integrated on a semiconductor substrate.
Silicon is the material most commonly used for manufacturing advanced microelectronic devices. Current electronic manufacturing technology may be considered mature, but a new optical communication technology is emerging. In optical communication technology, basic information is carried by optical signals having standard wavelengths in a range between 1.3 and 1.55 microns.
It would be highly desirable to combine optical and electronic functions in silicon to implement optical-electronic applications in a single semiconductor device. Significant progress has recently been made in the combination of electronic and optical technologies for manufacturing semiconductor optical devices operating at near infrared wavelengths.
A few examples may be found in the following three articles: 1) optical waveguides can be made with low losses, as disclosed by Fisher et al. in the IEEE article titled xe2x80x9cPhotonics Technology Lettersxe2x80x9d 8, 647 (1996); 2) light emitting diodes based on erbium (Er) doping have been demonstrated, as reported by Coffa et al. in the MRS Bulletin on xe2x80x9cSi-based optoelectronicsxe2x80x9d 23, 4, edited by Materials Research Society, S. Coffa and L. Tsybeskov guest editors; and 3) optical switches based on an electro-optic effect can be formed on silicon, as disclosed by Cutolo et al. in Lightwave Technology 15, 505 (1997)
There is, however, a main limitation for using silicon in optical applications such as, for example, optical interconnections intra-chip or between chips. This main limitation is due to the lack of a coherent light source, i.e., a silicon-based laser. Silicon is not suitable as an efficient light emission due to its indirect band gap.
Several approaches have been used to try to overcome this problem. The use of optical doping of silicon with rare earth ions, with or without impurities such as O, F, and N presents several interesting features not only for manufacturing efficient light emitting diodes, but also for the attempt of forming a silicon-based laser. Efficient room temperature electro-luminescence from erbium-oxygen co-doped silicon diodes has been reported. Moreover, the long spontaneous lifetime of the first excited state of erbium (about 1 ms), can insure a population inversion which is needed for an efficient light emission.
To fully understand all the aspects of the present invention, a schematic diagram of the mechanisms connected to electrical pumping of erbium ions are shown in FIGS. 1, 2a, 2b, 3a and 3b. A room temperature electro-luminescence at a 1.54 xcexcm wavelength can be achieved when Er ions are incorporated into a P/N diode junction.
A known approach is disclosed in U.S. Pat. No. 5,107,538 that relates to an optical waveguide system comprising a rare-earth Si-based optical device. This device, however, only produces a luminescence at a temperature close to 4 K and the efficiency of the light emission is extremely reduced at room temperature. Moreover, the ""538 patent fails to disclose the use of rare-earth ions located inside the junction. Therefore, the light emission obtained by this technology is insufficient for implementing commercial devices, and no electro-optical products on silicon are currently known to be on the market.
In view of the foregoing background, an object of the present invention is to provide a semiconductor device having structural and functional features to allow implementation of a coherent light emitting source into a semiconductor substrate that includes a rare-earth ions doped junction. The semiconductor substrate may be silicon.
Another object of the present invention is to allow optical interconnections intra-chip or between chips.
Yet another object of the present invention is to provide a single chip integrated semiconductor laser device. The semiconductor substrate may be silicon.
A further object of the present invention is to provide an electrically pumped optical amplification and laser action at room temperature.
These and other objects, advantages and features are provided by an electrically pumped optical amplification, and laser action using erbium-doped crystalline silicon. The semiconductor device according to the present invention comprises an erbium-doped P/N junction integrated within a semiconductor cavity or waveguide.
The invention allows combination of impact excitation of Er ions by hot carriers in the depletion layer of the reverse biased junction with a proper Er doping and electric field distribution. Electro-optical amplification is provided when the Er ions are within the depletion layer of the semiconductor device. The Er ions provide proper acceleration of the carriers before they enter the Er-doped region.
Accordingly, the present invention is directed to a semiconductor device, a semiconductor laser device, and a method for manufacturing a semiconductor device.